A consortium of seven laboratories is proposed to focus the power of modern molecular analysis and cell technology on the processes of genetic change induced by environmental mutagenic agents. Each of these laboratories is experienced in developing and applying its own peculiar set of genetic, cellular and molecular techniques to the study of gene mutation in bacterial, yeast, rodent and human cells. These techniques include means to measure the amount, identify the structure and specify the position in DNA of a variety of mutagenic reaction products. The consortium is also capable of isolating and characterizing novel mutants in the process of mutagenesis and investigating the biochemical genetics of constitutive and inducible responses to premutagenic damage in such variant cells. The proposed relation would be particularly strong in its ability to identify, isolate and sequence genes related to the processes of mutagenesis and to study the role of the products of such genes in the molecular biology of cell responses to mutagenic agents.